A method of making Si3N4 is disclosed herein involving adding agricultural husk material powder to a container, applying heat, and forming silicon nitride, wherein the silicon nitride is nanotubes and nanorods.
Silicon nitride, SiN, is an advanced ceramic material that has been in existence for many years but is finding important technological applications at extreme temperatures because of its high hardness, thermal conductivity, and resistance to erosion, corrosion and oxidation. SiN is also included among the family of reinforcement materials in metal matrix composites such as aluminum.
Indeed, components fabricated from SiC materials have surfaces that come close to the hardness of diamonds and possess excellent resistance to abrasion.
Nanocrystalline materials have mechanical properties that are largely governed by their ultimate sizes due to their large surface areas where most of the atoms are localized. Here, nanocrystalline/nanorods composites are produced that are superhard materials which will have promise for applications in the emerging field of miniaturized moving parts in microelectro-mechanical systems.
Silicon Nitride (Si3N4) is an important ceramic material for many technological applications due to its combination of exceptional physical, mechanical and electrical properties. Some of its unique mechanical properties include low density, high temperature strength, high hardness, excellent resistance to erosion, good fracture toughness, mechanical fatigue and creep resistance, and good corrosion and oxidation resistance.
In addition to mechanical properties, Si3N4 is a wide gap semiconductor and is used in electronics applications as an insulator and chemical barrier in integrated circuits. When used as a passivation layer for microchips, it acts as a diffusion barrier against water molecules and sodium ions and thus prevents corrosion in microelectronics.
Other electronic applications of silicon nitride are found in xerographic processes, as an ignition source for domestic gas appliances, and as cantilevers in atomic force microscopes.
Wheat and rice are major agricultural crops which results in millions of tons of wheat and rice husks being produced as byproducts during the milling process and provide abundant renewable sources for a combination of carbonaceous and silica matter. The chemical compositions of the wheat and rice husks consist of high levels of silica content and organic (carbon) matter. The silica is present either in the amorphous or the crystalline phase. We have shown the formation of SiC nanoparticles, nanowires, nanorods or spherical colloids, through high temperature treatment in argon atmosphere or vacuum of wheat and rice husks, sorghum leaves, corn residues and/or the combination of carbon species, such as nanotubes, with silicate-containing species. It has been demonstrated that nanostructured silicon carbide results from the reaction between carbon and silica, intimately dispersed in these biomasses, when they go through carbothermal reaction in an inert atmosphere of argon or vacuum.
In this teaching, we will present results showing the formation of the α-phase of Si3N4 by carbothermal reduction of SiO2 in the presence of a nitrogen atmosphere in one-step process. The transmission electron microcroscopy and scanning electron microscopy results indicate the formation of nanostructures such as nanorods, nanotubues and nanoparticles of Si3N4. Moreover, in a two-step process in which SiC was produced from either rice or wheat husk and followed by treating in nitrogen at 1450 C, our results show that the processed sample results in a composite having α- and β-phases of Si3N4 and the cubic phase of SiC.